1 // This file is Copyright its original authors, visible in version control
4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
7 // You may not use this file except in accordance with one or both of these
10 //! Feature flag definitions for the Lightning protocol according to [BOLT #9].
12 //! Lightning nodes advertise a supported set of operation through feature flags. Features are
13 //! applicable for a specific context as indicated in some [messages]. [`Features`] encapsulates
14 //! behavior for specifying and checking feature flags for a particular context. Each feature is
15 //! defined internally by a trait specifying the corresponding flags (i.e., even and odd bits).
17 //! Whether a feature is considered "known" or "unknown" is relative to the implementation, whereas
18 //! the term "supports" is used in reference to a particular set of [`Features`]. That is, a node
19 //! supports a feature if it advertises the feature (as either required or optional) to its peers.
20 //! And the implementation can interpret a feature if the feature is known to it.
22 //! The following features are currently required in the LDK:
23 //! - `VariableLengthOnion` - requires/supports variable-length routing onion payloads
24 //! (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md) for more information).
25 //! - `StaticRemoteKey` - requires/supports static key for remote output
26 //! (see [BOLT-3](https://github.com/lightning/bolts/blob/master/03-transactions.md) for more information).
28 //! The following features are currently supported in the LDK:
29 //! - `DataLossProtect` - requires/supports that a node which has somehow fallen behind, e.g., has been restored from an old backup,
30 //! can detect that it has fallen behind
31 //! (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
32 //! - `InitialRoutingSync` - requires/supports that the sending node needs a complete routing information dump
33 //! (see [BOLT-7](https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#initial-sync) for more information).
34 //! - `UpfrontShutdownScript` - commits to a shutdown scriptpubkey when opening a channel
35 //! (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-open_channel-message) for more information).
36 //! - `GossipQueries` - requires/supports more sophisticated gossip control
37 //! (see [BOLT-7](https://github.com/lightning/bolts/blob/master/07-routing-gossip.md) for more information).
38 //! - `PaymentSecret` - requires/supports that a node supports payment_secret field
39 //! (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md) for more information).
40 //! - `BasicMPP` - requires/supports that a node can receive basic multi-part payments
41 //! (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md#basic-multi-part-payments) for more information).
42 //! - `Wumbo` - requires/supports that a node create large channels. Called `option_support_large_channel` in the spec.
43 //! (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-open_channel-message) for more information).
44 //! - `ShutdownAnySegwit` - requires/supports that future segwit versions are allowed in `shutdown`
45 //! (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
46 //! - `OnionMessages` - requires/supports forwarding onion messages
47 //! (see [BOLT-7](https://github.com/lightning/bolts/pull/759/files) for more information).
49 //! - `ChannelType` - node supports the channel_type field in open/accept
50 //! (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
51 //! - `SCIDPrivacy` - supply channel aliases for routing
52 //! (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
53 //! - `PaymentMetadata` - include additional data in invoices which is passed to recipients in the
55 //! (see [BOLT-11](https://github.com/lightning/bolts/blob/master/11-payment-encoding.md) for
57 //! - `ZeroConf` - supports accepting HTLCs and using channels prior to funding confirmation
59 //! [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-channel_ready-message)
61 //! - `Keysend` - send funds to a node without an invoice
62 //! (see the [`Keysend` feature assignment proposal](https://github.com/lightning/bolts/issues/605#issuecomment-606679798) for more information).
63 //! - `AnchorsZeroFeeHtlcTx` - requires/supports that commitment transactions include anchor outputs
64 //! and HTLC transactions are pre-signed with zero fee (see
65 //! [BOLT-3](https://github.com/lightning/bolts/blob/master/03-transactions.md) for more
68 //! LDK knows about the following features, but does not support them:
69 //! - `AnchorsNonzeroFeeHtlcTx` - the initial version of anchor outputs, which was later found to be
70 //! vulnerable (see this
71 //! [mailing list post](https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-September/002796.html)
72 //! for more information).
74 //! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
75 //! [messages]: crate::ln::msgs
77 use crate::{io, io_extras};
78 use crate::prelude::*;
80 use core::borrow::Borrow;
81 use core::hash::{Hash, Hasher};
82 use core::marker::PhantomData;
85 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
86 use crate::ln::msgs::DecodeError;
87 use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
90 use crate::prelude::*;
91 use crate::ln::features::Features;
93 /// The context in which [`Features`] are applicable. Defines which features are known to the
94 /// implementation, though specification of them as required or optional is up to the code
95 /// constructing a features object.
97 /// Bitmask for selecting features that are known to the implementation.
98 const KNOWN_FEATURE_MASK: &'static [u8];
101 /// Defines a [`Context`] by stating which features it requires and which are optional. Features
102 /// are specified as a comma-separated list of bytes where each byte is a pipe-delimited list of
103 /// feature identifiers.
104 macro_rules! define_context {
105 ($context: ident, [$( $( $known_feature: ident )|*, )*]) => {
106 #[derive(Eq, PartialEq)]
107 pub struct $context {}
109 impl Context for $context {
110 const KNOWN_FEATURE_MASK: &'static [u8] = &[
113 <Self as $known_feature>::REQUIRED_MASK |
114 <Self as $known_feature>::OPTIONAL_MASK)*,
119 impl alloc::fmt::Display for Features<$context> {
120 fn fmt(&self, fmt: &mut alloc::fmt::Formatter) -> Result<(), alloc::fmt::Error> {
123 fmt.write_fmt(format_args!("{}: {}, ", stringify!($known_feature),
124 if <$context as $known_feature>::requires_feature(&self.flags) { "required" }
125 else if <$context as $known_feature>::supports_feature(&self.flags) { "supported" }
126 else { "not supported" }))?;
128 {} // Rust gets mad if we only have a $()* block here, so add a dummy {}
130 fmt.write_fmt(format_args!("unknown flags: {}",
131 if self.requires_unknown_bits() { "required" }
132 else if self.supports_unknown_bits() { "supported" } else { "none" }))
138 define_context!(InitContext, [
140 DataLossProtect | InitialRoutingSync | UpfrontShutdownScript | GossipQueries,
142 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
144 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
150 ChannelType | SCIDPrivacy,
154 define_context!(NodeContext, [
156 DataLossProtect | UpfrontShutdownScript | GossipQueries,
158 VariableLengthOnion | StaticRemoteKey | PaymentSecret,
160 BasicMPP | Wumbo | AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
166 ChannelType | SCIDPrivacy,
170 define_context!(ChannelContext, []);
171 define_context!(Bolt11InvoiceContext, [
175 VariableLengthOnion | PaymentSecret,
187 define_context!(OfferContext, []);
188 define_context!(InvoiceRequestContext, []);
189 define_context!(Bolt12InvoiceContext, [
197 define_context!(BlindedHopContext, []);
198 // This isn't a "real" feature context, and is only used in the channel_type field in an
199 // `OpenChannel` message.
200 define_context!(ChannelTypeContext, [
206 AnchorsNonzeroFeeHtlcTx | AnchorsZeroFeeHtlcTx,
217 /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
218 /// useful for manipulating feature flags.
219 macro_rules! define_feature {
220 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
221 $required_setter: ident, $supported_getter: ident) => {
224 /// See [BOLT #9] for details.
226 /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
227 pub trait $feature: Context {
228 /// The bit used to signify that the feature is required.
229 const EVEN_BIT: usize = $odd_bit - 1;
231 /// The bit used to signify that the feature is optional.
232 const ODD_BIT: usize = $odd_bit;
234 /// Assertion that [`EVEN_BIT`] is actually even.
236 /// [`EVEN_BIT`]: #associatedconstant.EVEN_BIT
237 const ASSERT_EVEN_BIT_PARITY: usize;
239 /// Assertion that [`ODD_BIT`] is actually odd.
241 /// [`ODD_BIT`]: #associatedconstant.ODD_BIT
242 const ASSERT_ODD_BIT_PARITY: usize;
244 /// Assertion that the bits are set in the context's [`KNOWN_FEATURE_MASK`].
246 /// [`KNOWN_FEATURE_MASK`]: Context::KNOWN_FEATURE_MASK
247 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
248 const ASSERT_BITS_IN_MASK: u8;
250 /// The byte where the feature is set.
251 const BYTE_OFFSET: usize = Self::EVEN_BIT / 8;
253 /// The bitmask for the feature's required flag relative to the [`BYTE_OFFSET`].
255 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
256 const REQUIRED_MASK: u8 = 1 << (Self::EVEN_BIT - 8 * Self::BYTE_OFFSET);
258 /// The bitmask for the feature's optional flag relative to the [`BYTE_OFFSET`].
260 /// [`BYTE_OFFSET`]: #associatedconstant.BYTE_OFFSET
261 const OPTIONAL_MASK: u8 = 1 << (Self::ODD_BIT - 8 * Self::BYTE_OFFSET);
263 /// Returns whether the feature is required by the given flags.
265 fn requires_feature(flags: &Vec<u8>) -> bool {
266 flags.len() > Self::BYTE_OFFSET &&
267 (flags[Self::BYTE_OFFSET] & Self::REQUIRED_MASK) != 0
270 /// Returns whether the feature is supported by the given flags.
272 fn supports_feature(flags: &Vec<u8>) -> bool {
273 flags.len() > Self::BYTE_OFFSET &&
274 (flags[Self::BYTE_OFFSET] & (Self::REQUIRED_MASK | Self::OPTIONAL_MASK)) != 0
277 /// Sets the feature's required (even) bit in the given flags.
279 fn set_required_bit(flags: &mut Vec<u8>) {
280 if flags.len() <= Self::BYTE_OFFSET {
281 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
284 flags[Self::BYTE_OFFSET] |= Self::REQUIRED_MASK;
285 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
288 /// Sets the feature's optional (odd) bit in the given flags.
290 fn set_optional_bit(flags: &mut Vec<u8>) {
291 if flags.len() <= Self::BYTE_OFFSET {
292 flags.resize(Self::BYTE_OFFSET + 1, 0u8);
295 flags[Self::BYTE_OFFSET] |= Self::OPTIONAL_MASK;
298 /// Clears the feature's required (even) and optional (odd) bits from the given
301 fn clear_bits(flags: &mut Vec<u8>) {
302 if flags.len() > Self::BYTE_OFFSET {
303 flags[Self::BYTE_OFFSET] &= !Self::REQUIRED_MASK;
304 flags[Self::BYTE_OFFSET] &= !Self::OPTIONAL_MASK;
307 let last_non_zero_byte = flags.iter().rposition(|&byte| byte != 0);
308 let size = if let Some(offset) = last_non_zero_byte { offset + 1 } else { 0 };
309 flags.resize(size, 0u8);
313 impl <T: $feature> Features<T> {
314 /// Set this feature as optional.
315 pub fn $optional_setter(&mut self) {
316 <T as $feature>::set_optional_bit(&mut self.flags);
319 /// Set this feature as required.
320 pub fn $required_setter(&mut self) {
321 <T as $feature>::set_required_bit(&mut self.flags);
324 /// Checks if this feature is supported.
325 pub fn $supported_getter(&self) -> bool {
326 <T as $feature>::supports_feature(&self.flags)
331 impl $feature for $context {
333 const ASSERT_EVEN_BIT_PARITY: usize = 0 - (<Self as $feature>::EVEN_BIT % 2);
336 const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
338 // (byte & (REQUIRED_MASK | OPTIONAL_MASK)) >> (EVEN_BIT % 8) == 3
339 #[cfg(not(test))] // We violate this constraint with `UnknownFeature`
340 const ASSERT_BITS_IN_MASK: u8 =
341 ((<$context>::KNOWN_FEATURE_MASK[<Self as $feature>::BYTE_OFFSET] & (<Self as $feature>::REQUIRED_MASK | <Self as $feature>::OPTIONAL_MASK))
342 >> (<Self as $feature>::EVEN_BIT % 8)) - 3;
346 ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
347 $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
348 define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
349 impl <T: $feature> Features<T> {
350 /// Checks if this feature is required.
351 pub fn $required_getter(&self) -> bool {
352 <T as $feature>::requires_feature(&self.flags)
358 define_feature!(1, DataLossProtect, [InitContext, NodeContext],
359 "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
360 set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
361 // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
362 define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
363 set_initial_routing_sync_optional, set_initial_routing_sync_required,
364 initial_routing_sync);
365 define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
366 "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
367 set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
368 requires_upfront_shutdown_script);
369 define_feature!(7, GossipQueries, [InitContext, NodeContext],
370 "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
371 supports_gossip_queries, requires_gossip_queries);
372 define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, Bolt11InvoiceContext],
373 "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
374 set_variable_length_onion_required, supports_variable_length_onion,
375 requires_variable_length_onion);
376 define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
377 "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
378 set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
379 define_feature!(15, PaymentSecret, [InitContext, NodeContext, Bolt11InvoiceContext],
380 "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
381 supports_payment_secret, requires_payment_secret);
382 define_feature!(17, BasicMPP, [InitContext, NodeContext, Bolt11InvoiceContext, Bolt12InvoiceContext],
383 "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
384 supports_basic_mpp, requires_basic_mpp);
385 define_feature!(19, Wumbo, [InitContext, NodeContext],
386 "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
387 supports_wumbo, requires_wumbo);
388 define_feature!(21, AnchorsNonzeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
389 "Feature flags for `option_anchors_nonzero_fee_htlc_tx`.", set_anchors_nonzero_fee_htlc_tx_optional,
390 set_anchors_nonzero_fee_htlc_tx_required, supports_anchors_nonzero_fee_htlc_tx, requires_anchors_nonzero_fee_htlc_tx);
391 define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
392 "Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
393 set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
394 define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
395 "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
396 set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
397 define_feature!(39, OnionMessages, [InitContext, NodeContext],
398 "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
399 set_onion_messages_required, supports_onion_messages, requires_onion_messages);
400 define_feature!(45, ChannelType, [InitContext, NodeContext],
401 "Feature flags for `option_channel_type`.", set_channel_type_optional,
402 set_channel_type_required, supports_channel_type, requires_channel_type);
403 define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
404 "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
405 set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
406 define_feature!(49, PaymentMetadata, [Bolt11InvoiceContext],
407 "Feature flags for payment metadata in invoices.", set_payment_metadata_optional,
408 set_payment_metadata_required, supports_payment_metadata, requires_payment_metadata);
409 define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
410 "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
411 set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
412 define_feature!(55, Keysend, [NodeContext],
413 "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
414 supports_keysend, requires_keysend);
415 // Note: update the module-level docs when a new feature bit is added!
418 define_feature!(123456789, UnknownFeature,
419 [NodeContext, ChannelContext, Bolt11InvoiceContext, OfferContext, InvoiceRequestContext, Bolt12InvoiceContext, BlindedHopContext],
420 "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
421 set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
424 /// Tracks the set of features which a node implements, templated by the context in which it
427 /// This is not exported to bindings users as we map the concrete feature types below directly instead
429 pub struct Features<T: sealed::Context> {
430 /// Note that, for convenience, flags is LITTLE endian (despite being big-endian on the wire)
432 mark: PhantomData<T>,
435 /// This is not exported to bindings users but probably should be.
436 impl<T: sealed::Context, Rhs: Borrow<Self>> core::ops::BitOrAssign<Rhs> for Features<T> {
437 fn bitor_assign(&mut self, rhs: Rhs) {
438 let total_feature_len = cmp::max(self.flags.len(), rhs.borrow().flags.len());
439 self.flags.resize(total_feature_len, 0u8);
440 for (byte, rhs_byte) in self.flags.iter_mut().zip(rhs.borrow().flags.iter()) {
446 /// This is not exported to bindings users but probably should be.
447 impl<T: sealed::Context> core::ops::BitOr for Features<T> {
450 fn bitor(mut self, o: Self) -> Self {
456 impl<T: sealed::Context> Clone for Features<T> {
457 fn clone(&self) -> Self {
459 flags: self.flags.clone(),
464 impl<T: sealed::Context> Hash for Features<T> {
465 fn hash<H: Hasher>(&self, hasher: &mut H) {
466 self.flags.hash(hasher);
469 impl<T: sealed::Context> PartialEq for Features<T> {
470 fn eq(&self, o: &Self) -> bool {
471 self.flags.eq(&o.flags)
474 impl<T: sealed::Context> PartialOrd for Features<T> {
475 fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
476 self.flags.partial_cmp(&other.flags)
479 impl<T: sealed::Context + Eq> Ord for Features<T> {
480 fn cmp(&self, other: &Self) -> cmp::Ordering {
481 self.flags.cmp(&other.flags)
484 impl<T: sealed::Context> fmt::Debug for Features<T> {
485 fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
490 /// Features used within an `init` message.
491 pub type InitFeatures = Features<sealed::InitContext>;
492 /// Features used within a `node_announcement` message.
493 pub type NodeFeatures = Features<sealed::NodeContext>;
494 /// Features used within a `channel_announcement` message.
495 pub type ChannelFeatures = Features<sealed::ChannelContext>;
496 /// Features used within an invoice.
497 pub type Bolt11InvoiceFeatures = Features<sealed::Bolt11InvoiceContext>;
498 /// Features used within an `offer`.
499 pub type OfferFeatures = Features<sealed::OfferContext>;
500 /// Features used within an `invoice_request`.
501 pub type InvoiceRequestFeatures = Features<sealed::InvoiceRequestContext>;
502 /// Features used within an `invoice`.
503 pub type Bolt12InvoiceFeatures = Features<sealed::Bolt12InvoiceContext>;
504 /// Features used within BOLT 4 encrypted_data_tlv and BOLT 12 blinded_payinfo
505 pub type BlindedHopFeatures = Features<sealed::BlindedHopContext>;
507 /// Features used within the channel_type field in an OpenChannel message.
509 /// A channel is always of some known "type", describing the transaction formats used and the exact
510 /// semantics of our interaction with our peer.
512 /// Note that because a channel is a specific type which is proposed by the opener and accepted by
513 /// the counterparty, only required features are allowed here.
515 /// This is serialized differently from other feature types - it is not prefixed by a length, and
516 /// thus must only appear inside a TLV where its length is known in advance.
517 pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
520 /// Writes all features present up to, and including, 13.
521 pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
522 let len = cmp::min(2, self.flags.len());
523 (len as u16).write(w)?;
524 for i in (0..len).rev() {
526 self.flags[i].write(w)?;
528 // On byte 1, we want up-to-and-including-bit-13, 0-indexed, which is
529 // up-to-and-including-bit-5, 0-indexed, on this byte:
530 (self.flags[i] & 0b00_11_11_11).write(w)?;
536 /// Converts `InitFeatures` to `Features<C>`. Only known `InitFeatures` relevant to context `C`
537 /// are included in the result.
538 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
539 self.to_context_internal()
543 impl Bolt11InvoiceFeatures {
544 /// Converts `Bolt11InvoiceFeatures` to `Features<C>`. Only known `Bolt11InvoiceFeatures` relevant to
545 /// context `C` are included in the result.
546 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
547 self.to_context_internal()
550 /// Getting a route for a keysend payment to a private node requires providing the payee's
551 /// features (since they were not announced in a node announcement). However, keysend payments
552 /// don't have an invoice to pull the payee's features from, so this method is provided for use in
553 /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
554 /// `Bolt11InvoiceFeatures` for [`find_route`].
556 /// MPP keysend is not widely supported yet, so we parameterize support to allow the user to
557 /// choose whether their router should find multi-part routes.
559 /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
560 /// [`find_route`]: crate::routing::router::find_route
561 pub(crate) fn for_keysend(allow_mpp: bool) -> Bolt11InvoiceFeatures {
562 let mut res = Bolt11InvoiceFeatures::empty();
563 res.set_variable_length_onion_optional();
565 res.set_basic_mpp_optional();
571 impl Bolt12InvoiceFeatures {
572 /// Converts [`Bolt12InvoiceFeatures`] to [`Features<C>`]. Only known [`Bolt12InvoiceFeatures`]
573 /// relevant to context `C` are included in the result.
574 pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
575 self.to_context_internal()
579 impl ChannelTypeFeatures {
580 // Maps the relevant `InitFeatures` to `ChannelTypeFeatures`. Any unknown features to
581 // `ChannelTypeFeatures` are not included in the result.
582 pub(crate) fn from_init(init: &InitFeatures) -> Self {
583 let mut ret = init.to_context_internal();
584 // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
585 // optional bits and then AND out the optional ones.
586 for byte in ret.flags.iter_mut() {
587 *byte |= (*byte & 0b10_10_10_10) >> 1;
588 *byte &= 0b01_01_01_01;
593 /// Constructs a ChannelTypeFeatures with only static_remotekey set
594 pub(crate) fn only_static_remote_key() -> Self {
595 let mut ret = Self::empty();
596 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
600 /// Constructs a ChannelTypeFeatures with anchors support
601 pub(crate) fn anchors_zero_htlc_fee_and_dependencies() -> Self {
602 let mut ret = Self::empty();
603 <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
604 <sealed::ChannelTypeContext as sealed::AnchorsZeroFeeHtlcTx>::set_required_bit(&mut ret.flags);
609 impl ToBase32 for Bolt11InvoiceFeatures {
610 fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
611 // Explanation for the "4": the normal way to round up when dividing is to add the divisor
612 // minus one before dividing
613 let length_u5s = (self.flags.len() * 8 + 4) / 5 as usize;
614 let mut res_u5s: Vec<u5> = vec![u5::try_from_u8(0).unwrap(); length_u5s];
615 for (byte_idx, byte) in self.flags.iter().enumerate() {
616 let bit_pos_from_left_0_indexed = byte_idx * 8;
617 let new_u5_idx = length_u5s - (bit_pos_from_left_0_indexed / 5) as usize - 1;
618 let new_bit_pos = bit_pos_from_left_0_indexed % 5;
619 let shifted_chunk_u16 = (*byte as u16) << new_bit_pos;
620 let curr_u5_as_u8 = res_u5s[new_u5_idx].to_u8();
621 res_u5s[new_u5_idx] = u5::try_from_u8(curr_u5_as_u8 | ((shifted_chunk_u16 & 0x001f) as u8)).unwrap();
623 let curr_u5_as_u8 = res_u5s[new_u5_idx - 1].to_u8();
624 res_u5s[new_u5_idx - 1] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 5) & 0x001f) as u8)).unwrap();
627 let curr_u5_as_u8 = res_u5s[new_u5_idx - 2].to_u8();
628 res_u5s[new_u5_idx - 2] = u5::try_from_u8(curr_u5_as_u8 | (((shifted_chunk_u16 >> 10) & 0x001f) as u8)).unwrap();
631 // Trim the highest feature bits.
632 while !res_u5s.is_empty() && res_u5s[0] == u5::try_from_u8(0).unwrap() {
635 writer.write(&res_u5s)
639 impl Base32Len for Bolt11InvoiceFeatures {
640 fn base32_len(&self) -> usize {
641 self.to_base32().len()
645 impl FromBase32 for Bolt11InvoiceFeatures {
646 type Err = bech32::Error;
648 fn from_base32(field_data: &[u5]) -> Result<Bolt11InvoiceFeatures, bech32::Error> {
649 // Explanation for the "7": the normal way to round up when dividing is to add the divisor
650 // minus one before dividing
651 let length_bytes = (field_data.len() * 5 + 7) / 8 as usize;
652 let mut res_bytes: Vec<u8> = vec![0; length_bytes];
653 for (u5_idx, chunk) in field_data.iter().enumerate() {
654 let bit_pos_from_right_0_indexed = (field_data.len() - u5_idx - 1) * 5;
655 let new_byte_idx = (bit_pos_from_right_0_indexed / 8) as usize;
656 let new_bit_pos = bit_pos_from_right_0_indexed % 8;
657 let chunk_u16 = chunk.to_u8() as u16;
658 res_bytes[new_byte_idx] |= ((chunk_u16 << new_bit_pos) & 0xff) as u8;
659 if new_byte_idx != length_bytes - 1 {
660 res_bytes[new_byte_idx + 1] |= ((chunk_u16 >> (8-new_bit_pos)) & 0xff) as u8;
663 // Trim the highest feature bits.
664 while !res_bytes.is_empty() && res_bytes[res_bytes.len() - 1] == 0 {
667 Ok(Bolt11InvoiceFeatures::from_le_bytes(res_bytes))
671 impl<T: sealed::Context> Features<T> {
672 /// Create a blank Features with no features set
673 pub fn empty() -> Self {
680 /// Converts `Features<T>` to `Features<C>`. Only known `T` features relevant to context `C` are
681 /// included in the result.
682 fn to_context_internal<C: sealed::Context>(&self) -> Features<C> {
683 let from_byte_count = T::KNOWN_FEATURE_MASK.len();
684 let to_byte_count = C::KNOWN_FEATURE_MASK.len();
685 let mut flags = Vec::new();
686 for (i, byte) in self.flags.iter().enumerate() {
687 if i < from_byte_count && i < to_byte_count {
688 let from_known_features = T::KNOWN_FEATURE_MASK[i];
689 let to_known_features = C::KNOWN_FEATURE_MASK[i];
690 flags.push(byte & from_known_features & to_known_features);
693 Features::<C> { flags, mark: PhantomData, }
696 /// Create a Features given a set of flags, in little-endian. This is in reverse byte order from
697 /// most on-the-wire encodings.
699 /// This is not exported to bindings users as we don't support export across multiple T
700 pub fn from_le_bytes(flags: Vec<u8>) -> Features<T> {
708 /// Gets the underlying flags set, in LE.
709 pub fn le_flags(&self) -> &Vec<u8> {
713 fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
714 for f in self.flags.iter().rev() { // Swap back to big-endian
720 fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
721 flags.reverse(); // Swap to little-endian
728 pub(crate) fn supports_any_optional_bits(&self) -> bool {
729 self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
732 /// Returns true if this `Features` object contains required features unknown by `other`.
733 pub fn requires_unknown_bits_from(&self, other: &Self) -> bool {
734 // Bitwise AND-ing with all even bits set except for known features will select required
736 self.flags.iter().enumerate().any(|(i, &byte)| {
737 const REQUIRED_FEATURES: u8 = 0b01_01_01_01;
738 const OPTIONAL_FEATURES: u8 = 0b10_10_10_10;
739 let unknown_features = if i < other.flags.len() {
740 // Form a mask similar to !T::KNOWN_FEATURE_MASK only for `other`
742 | ((other.flags[i] >> 1) & REQUIRED_FEATURES)
743 | ((other.flags[i] << 1) & OPTIONAL_FEATURES))
747 (byte & (REQUIRED_FEATURES & unknown_features)) != 0
751 /// Returns true if this `Features` object contains unknown feature flags which are set as
753 pub fn requires_unknown_bits(&self) -> bool {
754 // Bitwise AND-ing with all even bits set except for known features will select required
756 let byte_count = T::KNOWN_FEATURE_MASK.len();
757 self.flags.iter().enumerate().any(|(i, &byte)| {
758 let required_features = 0b01_01_01_01;
759 let unknown_features = if i < byte_count {
760 !T::KNOWN_FEATURE_MASK[i]
764 (byte & (required_features & unknown_features)) != 0
768 pub(crate) fn supports_unknown_bits(&self) -> bool {
769 // Bitwise AND-ing with all even and odd bits set except for known features will select
770 // both required and optional unknown features.
771 let byte_count = T::KNOWN_FEATURE_MASK.len();
772 self.flags.iter().enumerate().any(|(i, &byte)| {
773 let unknown_features = if i < byte_count {
774 !T::KNOWN_FEATURE_MASK[i]
778 (byte & unknown_features) != 0
782 // Returns true if the features within `self` are a subset of the features within `other`.
783 pub(crate) fn is_subset(&self, other: &Self) -> bool {
784 for (idx, byte) in self.flags.iter().enumerate() {
785 if let Some(other_byte) = other.flags.get(idx) {
786 if byte & other_byte != *byte {
787 // `self` has bits set that `other` doesn't.
792 // `self` has a non-zero byte that `other` doesn't.
800 /// Sets a required custom feature bit. Errors if `bit` is outside the custom range as defined
801 /// by [bLIP 2] or if it is a known `T` feature.
803 /// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
804 /// be set instead (i.e., `bit - 1`).
806 /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
807 pub fn set_required_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
808 self.set_custom_bit(bit - (bit % 2))
811 /// Sets an optional custom feature bit. Errors if `bit` is outside the custom range as defined
812 /// by [bLIP 2] or if it is a known `T` feature.
814 /// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
815 /// set instead (i.e., `bit + 1`).
817 /// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
818 pub fn set_optional_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
819 self.set_custom_bit(bit + (1 - (bit % 2)))
822 fn set_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
827 let byte_offset = bit / 8;
828 let mask = 1 << (bit - 8 * byte_offset);
829 if byte_offset < T::KNOWN_FEATURE_MASK.len() {
830 if (T::KNOWN_FEATURE_MASK[byte_offset] & mask) != 0 {
835 if self.flags.len() <= byte_offset {
836 self.flags.resize(byte_offset + 1, 0u8);
839 self.flags[byte_offset] |= mask;
845 impl<T: sealed::UpfrontShutdownScript> Features<T> {
847 pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
848 <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
853 impl<T: sealed::ShutdownAnySegwit> Features<T> {
855 pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
856 <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
861 impl<T: sealed::Wumbo> Features<T> {
863 pub(crate) fn clear_wumbo(mut self) -> Self {
864 <T as sealed::Wumbo>::clear_bits(&mut self.flags);
869 impl<T: sealed::SCIDPrivacy> Features<T> {
870 pub(crate) fn clear_scid_privacy(&mut self) {
871 <T as sealed::SCIDPrivacy>::clear_bits(&mut self.flags);
875 impl<T: sealed::AnchorsZeroFeeHtlcTx> Features<T> {
876 pub(crate) fn clear_anchors_zero_fee_htlc_tx(&mut self) {
877 <T as sealed::AnchorsZeroFeeHtlcTx>::clear_bits(&mut self.flags);
882 impl<T: sealed::UnknownFeature> Features<T> {
883 pub(crate) fn unknown() -> Self {
884 let mut features = Self::empty();
885 features.set_unknown_feature_required();
890 macro_rules! impl_feature_len_prefixed_write {
891 ($features: ident) => {
892 impl Writeable for $features {
893 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
894 (self.flags.len() as u16).write(w)?;
898 impl Readable for $features {
899 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
900 Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
905 impl_feature_len_prefixed_write!(InitFeatures);
906 impl_feature_len_prefixed_write!(ChannelFeatures);
907 impl_feature_len_prefixed_write!(NodeFeatures);
908 impl_feature_len_prefixed_write!(Bolt11InvoiceFeatures);
909 impl_feature_len_prefixed_write!(Bolt12InvoiceFeatures);
910 impl_feature_len_prefixed_write!(BlindedHopFeatures);
912 // Some features only appear inside of TLVs, so they don't have a length prefix when serialized.
913 macro_rules! impl_feature_tlv_write {
914 ($features: ident) => {
915 impl Writeable for $features {
916 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
917 WithoutLength(self).write(w)
920 impl Readable for $features {
921 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
922 Ok(WithoutLength::<Self>::read(r)?.0)
928 impl_feature_tlv_write!(ChannelTypeFeatures);
930 // Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
931 // requires a length but the former does not.
933 impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
934 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
939 impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
940 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
941 let v = io_extras::read_to_end(r)?;
942 Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
948 use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, Bolt11InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
949 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
950 use crate::util::ser::{Readable, WithoutLength, Writeable};
953 fn sanity_test_unknown_bits() {
954 let features = ChannelFeatures::empty();
955 assert!(!features.requires_unknown_bits());
956 assert!(!features.supports_unknown_bits());
958 let mut features = ChannelFeatures::empty();
959 features.set_unknown_feature_required();
960 assert!(features.requires_unknown_bits());
961 assert!(features.supports_unknown_bits());
963 let mut features = ChannelFeatures::empty();
964 features.set_unknown_feature_optional();
965 assert!(!features.requires_unknown_bits());
966 assert!(features.supports_unknown_bits());
970 fn requires_unknown_bits_from() {
971 let mut features1 = InitFeatures::empty();
972 let mut features2 = InitFeatures::empty();
973 assert!(!features1.requires_unknown_bits_from(&features2));
974 assert!(!features2.requires_unknown_bits_from(&features1));
976 features1.set_data_loss_protect_required();
977 assert!(features1.requires_unknown_bits_from(&features2));
978 assert!(!features2.requires_unknown_bits_from(&features1));
980 features2.set_data_loss_protect_optional();
981 assert!(!features1.requires_unknown_bits_from(&features2));
982 assert!(!features2.requires_unknown_bits_from(&features1));
984 features2.set_gossip_queries_required();
985 assert!(!features1.requires_unknown_bits_from(&features2));
986 assert!(features2.requires_unknown_bits_from(&features1));
988 features1.set_gossip_queries_optional();
989 assert!(!features1.requires_unknown_bits_from(&features2));
990 assert!(!features2.requires_unknown_bits_from(&features1));
992 features1.set_variable_length_onion_required();
993 assert!(features1.requires_unknown_bits_from(&features2));
994 assert!(!features2.requires_unknown_bits_from(&features1));
996 features2.set_variable_length_onion_optional();
997 assert!(!features1.requires_unknown_bits_from(&features2));
998 assert!(!features2.requires_unknown_bits_from(&features1));
1000 features1.set_basic_mpp_required();
1001 features2.set_wumbo_required();
1002 assert!(features1.requires_unknown_bits_from(&features2));
1003 assert!(features2.requires_unknown_bits_from(&features1));
1007 fn convert_to_context_with_relevant_flags() {
1008 let mut init_features = InitFeatures::empty();
1009 // Set a bunch of features we use, plus initial_routing_sync_required (which shouldn't get
1010 // converted as it's only relevant in an init context).
1011 init_features.set_initial_routing_sync_required();
1012 init_features.set_data_loss_protect_required();
1013 init_features.set_variable_length_onion_required();
1014 init_features.set_static_remote_key_required();
1015 init_features.set_payment_secret_required();
1016 init_features.set_basic_mpp_optional();
1017 init_features.set_wumbo_optional();
1018 init_features.set_anchors_zero_fee_htlc_tx_optional();
1019 init_features.set_shutdown_any_segwit_optional();
1020 init_features.set_onion_messages_optional();
1021 init_features.set_channel_type_optional();
1022 init_features.set_scid_privacy_optional();
1023 init_features.set_zero_conf_optional();
1025 assert!(init_features.initial_routing_sync());
1026 assert!(!init_features.supports_upfront_shutdown_script());
1027 assert!(!init_features.supports_gossip_queries());
1029 let node_features: NodeFeatures = init_features.to_context();
1031 // Check that the flags are as expected:
1032 // - option_data_loss_protect (req)
1033 // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
1034 // - basic_mpp | wumbo | anchors_zero_fee_htlc_tx
1035 // - opt_shutdown_anysegwit
1037 // - option_channel_type | option_scid_alias
1038 // - option_zeroconf
1039 assert_eq!(node_features.flags.len(), 7);
1040 assert_eq!(node_features.flags[0], 0b00000001);
1041 assert_eq!(node_features.flags[1], 0b01010001);
1042 assert_eq!(node_features.flags[2], 0b10001010);
1043 assert_eq!(node_features.flags[3], 0b00001000);
1044 assert_eq!(node_features.flags[4], 0b10000000);
1045 assert_eq!(node_features.flags[5], 0b10100000);
1046 assert_eq!(node_features.flags[6], 0b00001000);
1049 // Check that cleared flags are kept blank when converting back:
1050 // - initial_routing_sync was not applicable to NodeContext
1051 // - upfront_shutdown_script was cleared before converting
1052 // - gossip_queries was cleared before converting
1053 let features: InitFeatures = node_features.to_context_internal();
1054 assert!(!features.initial_routing_sync());
1055 assert!(!features.supports_upfront_shutdown_script());
1056 assert!(!init_features.supports_gossip_queries());
1060 fn convert_to_context_with_unknown_flags() {
1061 // Ensure the `from` context has fewer known feature bytes than the `to` context.
1062 assert!(<sealed::ChannelContext as sealed::Context>::KNOWN_FEATURE_MASK.len() <
1063 <sealed::Bolt11InvoiceContext as sealed::Context>::KNOWN_FEATURE_MASK.len());
1064 let mut channel_features = ChannelFeatures::empty();
1065 channel_features.set_unknown_feature_optional();
1066 assert!(channel_features.supports_unknown_bits());
1067 let invoice_features: Bolt11InvoiceFeatures = channel_features.to_context_internal();
1068 assert!(!invoice_features.supports_unknown_bits());
1072 fn set_feature_bits() {
1073 let mut features = Bolt11InvoiceFeatures::empty();
1074 features.set_basic_mpp_optional();
1075 features.set_payment_secret_required();
1076 assert!(features.supports_basic_mpp());
1077 assert!(!features.requires_basic_mpp());
1078 assert!(features.requires_payment_secret());
1079 assert!(features.supports_payment_secret());
1083 fn set_custom_bits() {
1084 let mut features = Bolt11InvoiceFeatures::empty();
1085 features.set_variable_length_onion_optional();
1086 assert_eq!(features.flags[1], 0b00000010);
1088 assert!(features.set_optional_custom_bit(255).is_err());
1089 assert!(features.set_required_custom_bit(256).is_ok());
1090 assert!(features.set_required_custom_bit(258).is_ok());
1091 assert_eq!(features.flags[31], 0b00000000);
1092 assert_eq!(features.flags[32], 0b00000101);
1094 let known_bit = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::EVEN_BIT;
1095 let byte_offset = <sealed::Bolt11InvoiceContext as sealed::PaymentSecret>::BYTE_OFFSET;
1096 assert_eq!(byte_offset, 1);
1097 assert_eq!(features.flags[byte_offset], 0b00000010);
1098 assert!(features.set_required_custom_bit(known_bit).is_err());
1099 assert_eq!(features.flags[byte_offset], 0b00000010);
1101 let mut features = Bolt11InvoiceFeatures::empty();
1102 assert!(features.set_optional_custom_bit(256).is_ok());
1103 assert!(features.set_optional_custom_bit(259).is_ok());
1104 assert_eq!(features.flags[32], 0b00001010);
1106 let mut features = Bolt11InvoiceFeatures::empty();
1107 assert!(features.set_required_custom_bit(257).is_ok());
1108 assert!(features.set_required_custom_bit(258).is_ok());
1109 assert_eq!(features.flags[32], 0b00000101);
1113 fn encodes_features_without_length() {
1114 let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1115 assert_eq!(features.flags.len(), 8);
1117 let mut serialized_features = Vec::new();
1118 WithoutLength(&features).write(&mut serialized_features).unwrap();
1119 assert_eq!(serialized_features.len(), 8);
1121 let deserialized_features =
1122 WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
1123 assert_eq!(features, deserialized_features);
1127 fn invoice_features_encoding() {
1128 let features_as_u5s = vec![
1129 u5::try_from_u8(6).unwrap(),
1130 u5::try_from_u8(10).unwrap(),
1131 u5::try_from_u8(25).unwrap(),
1132 u5::try_from_u8(1).unwrap(),
1133 u5::try_from_u8(10).unwrap(),
1134 u5::try_from_u8(0).unwrap(),
1135 u5::try_from_u8(20).unwrap(),
1136 u5::try_from_u8(2).unwrap(),
1137 u5::try_from_u8(0).unwrap(),
1138 u5::try_from_u8(6).unwrap(),
1139 u5::try_from_u8(0).unwrap(),
1140 u5::try_from_u8(16).unwrap(),
1141 u5::try_from_u8(1).unwrap(),
1143 let features = Bolt11InvoiceFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
1145 // Test length calculation.
1146 assert_eq!(features.base32_len(), 13);
1148 // Test serialization.
1149 let features_serialized = features.to_base32();
1150 assert_eq!(features_as_u5s, features_serialized);
1152 // Test deserialization.
1153 let features_deserialized = Bolt11InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
1154 assert_eq!(features, features_deserialized);
1158 fn test_channel_type_mapping() {
1159 // If we map an Bolt11InvoiceFeatures with StaticRemoteKey optional, it should map into a
1160 // required-StaticRemoteKey ChannelTypeFeatures.
1161 let mut init_features = InitFeatures::empty();
1162 init_features.set_static_remote_key_optional();
1163 let converted_features = ChannelTypeFeatures::from_init(&init_features);
1164 assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
1165 assert!(!converted_features.supports_any_optional_bits());
1166 assert!(converted_features.requires_static_remote_key());